1. Field of the Invention
The present invention generally relates to a system for inspecting surface defects of a specimen and a method thereof, in particular to a system and a method for inspecting the surface defects of the wafer by using the scattered light.
2. Description of the Related Art
In field of semiconductor industry, it is important for the silicon substrate surface to be clean because the defects attached on the surface of the wafer will have great influence upon the chip manufacture process, such as the short circuit phenomenon. Therefore, inspecting the defects of the wafer surface becomes a significant issue in the chip manufacture process for increasing the yield rate and decreasing the cost of manufacturing process.
The wafer inspection systems which are used to detect surface defects on the silicon wafer can be divided into two types, the bright field (BF) system and the dark field (DF) system. In the BF system, the images of surface feature on wafer are obtained directly by using a camera and a microscope object lens, and the particle sizes can be measured rapidly and directly. In general, in order to acquire the image of micro-level particles, the higher magnification object lens, higher resolution image sensor, and shorter-wavelength light are required. Hence the cost of BF system will increase with the amount of its accessories, and its inspection speed becomes very slow due to the smaller inspection area. Since the DF system is able to collect the scattered light from the wafer surface, the size and number of particles can be evaluated from the intensity of scattered light. However, the DF system cannot get the real size of particles on the wafer surface, so it only can be applied to the inspection of bare wafer.